Evolution of the untouchables: Phylogenetics and classification of <i>Cnidoscolus</i> (Euphorbiaceae)

Maya‐Lastra, Carlos A.; Steinmann, Victor W.

doi:10.1002/tax.12093

Cited by 10 publications

(14 citation statements)

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“…I.M. Johnst (Euphorbiaceae) is a shrub of up to 5 m in height, distributed mainly in tropical America (Ross-Ibarra & Molina-Cruz 2002, Maya-Lastra & Steinmann 2019. C. aconitifolius is a monoecious plant species (i.e.…”

Section: Methodsmentioning

confidence: 99%

Domestication reduces phenotypic plasticity in chaya ( Cnidoscolus aconitifolius (Mill.) I.M. Johnst)

Munguía-Rosas

2021

Bot. Sci.

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Background: Natural selection optimizes phenotypic plasticity in plants found in environmentally variable habitats. However, it is unclear how artificial selection has affected the phenotypic plasticity of crops. Reduced plasticity in crop yield is often considered a desirable feature in cultivated plants; however, limited phenotypic plasticity in this and other traits may also affect the ability of crops to cope with environmental variation. Study species: Wild and domesticated chaya (Cnidoscolus aconitifolius (Mill.) I.M. Johnst). Question: How domestication has affected the phenotypic plasticity of vegetative traits in response to the light environment? Methods: Leaf area, leaf perimeter, leaf specific area, leaf production, trichome density, stem elongation, growth in stem diameter and slenderness were measured in clones of wild and domesticated plants. These clones were allocated to two contrasting light treatments: fully exposed to sun vs. placement beneath a shade cloth. The phenotypic traits and reaction norms were compared between the genotypes of wild and domesticated plants. Results: Lower plasticity in leaf production and slenderness was observed in the domesticated compared to the wild plants. Leaf production and slenderness are associated with the shade avoidance syndrome, which was evident in wild plants but not manifested in domesticated plants. Reduced plasticity in leaf production also suggests yield stability. Conclusion: Artificial selection reduces phenotypic plasticity in the yield of chaya and in its response to variation in light availability.

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Section: Methodsmentioning

confidence: 99%

Domestication reduces phenotypic plasticity in chaya ( Cnidoscolus aconitifolius (Mill.) I.M. Johnst)

Munguía-Rosas

2021

Bot. Sci.

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“…Euphorbiaceae (order Malphigiales) are another family with many urticant representatives. Cnidoscolus (tribe Manihoteae) ( Figure 5 e) is a large genus with nearly 100 species restricted to subtropical and tropical America [ 42 ]. Cnidoscolus is universally urticant, with the only exception of a non-stinging form of C. aconitifolius , which is an important green vegetable in northern Central America (“chaya”) [ 43 ].…”

Section: Stinging Hairsmentioning

confidence: 99%

Distribution, Ecology, Chemistry and Toxicology of Plant Stinging Hairs

Ensikat

Wessely

Engeser

et al. 2021

Toxins

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Plant stinging hairs have fascinated humans for time immemorial. True stinging hairs are highly specialized plant structures that are able to inject a physiologically active liquid into the skin and can be differentiated from irritant hairs (causing mechanical damage only). Stinging hairs can be classified into two basic types: Urtica-type stinging hairs with the classical “hypodermic syringe” mechanism expelling only liquid, and Tragia-type stinging hairs expelling a liquid together with a sharp crystal. In total, there are some 650 plant species with stinging hairs across five remotely related plant families (i.e., belonging to different plant orders). The family Urticaceae (order Rosales) includes a total of ca. 150 stinging representatives, amongst them the well-known stinging nettles (genus Urtica). There are also some 200 stinging species in Loasaceae (order Cornales), ca. 250 stinging species in Euphorbiaceae (order Malphigiales), a handful of species in Namaceae (order Boraginales), and one in Caricaceae (order Brassicales). Stinging hairs are commonly found on most aerial parts of the plants, especially the stem and leaves, but sometimes also on flowers and fruits. The ecological role of stinging hairs in plants seems to be essentially defense against mammalian herbivores, while they appear to be essentially inefficient against invertebrate pests. Stinging plants are therefore frequent pasture weeds across different taxa and geographical zones. Stinging hairs are usually combined with additional chemical and/or mechanical defenses in plants and are not a standalone mechanism. The physiological effects of stinging hairs on humans vary widely between stinging plants and range from a slight itch, skin rash (urticaria), and oedema to sharp pain and even serious neurological disorders such as neuropathy. Numerous studies have attempted to elucidate the chemical basis of the physiological effects. Since the middle of the 20th century, neurotransmitters (acetylcholine, histamine, serotonin) have been repeatedly detected in stinging hairs of Urticaceae, but recent analyses of Loasaceae stinging hair fluids revealed high variability in their composition and content of neurotransmitters. These substances can explain some of the physiological effects of stinging hairs, but fail to completely explain neuropathic effects, pointing to some yet unidentified neurotoxin. Inorganic ions (e.g., potassium) are detected in stinging hairs and could have synergistic effects. Very recently, ultrastable miniproteins dubbed “gympietides” have been reported from two species of Dendrocnide, arguably the most violently stinging plant. Gympietides are shown to be highly neurotoxic, providing a convincing explanation for Dendrocnide toxicity. For the roughly 648 remaining stinging plant species, similarly convincing data on toxicity are still lacking.

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“…Cnidoscolus aconitifolius (Euphorbiaceae) is a shrub native to Mexico and Central America 24,39 . It has been suggested that this plant was domesticated on the Yucatan Peninsula by the Maya where it is called "chaya" 40,41 .…”

Section: Study Speciesmentioning

confidence: 99%

“…In this study, I assessed the changes that the stems of chaya (Cnidoscolus aconitifolius), a clonal crop with edible leaves, have undergone through domestication. The closest wild relatives of this crop belong to the same species 24 . In contrast to their wild progenitors, the cultivar produces more, larger, non-stinging leaves, which have thicker stems that are used as propagules 25 .…”

Section: Introductionmentioning

confidence: 99%

Artificial Selection Optimizes Clonality in Chaya (Cnidoscolus Aconitifolius)

Munguía‐Rosas

2021

Preprint

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In angiosperms, clonality is a derived trait and is present in several wild and cultivated plant species. Therefore, over time, natural and artificial selection have optimized the novel function of being a propagule in organs whose previous function was exclusively vegetative. Although increased resource storage and resistance to desiccation have been suggested as the main adaptations for clonality in crops, there is little empirical evidence to support this assertion. Here, I assessed the changes that the stems of chaya (Cnidoscolus aconitifolius), a clonal crop, have undergone through domestication and evaluated their performance as propagules. To infer which traits have been optimized by artificial selection, I compared stem traits and their performance in root development and clone survival between wild and domesticated plants. I found that, relative to their wild ancestors, the stems of domesticated chaya have a greater storage capacity for water and starch. Additionally, the stems of domesticated plants produced more roots, shoots and leaves, and their clones lived longer. My results strongly suggest that artificial selection has optimized water and starch storage by stems in chaya. Because these traits also confer greater fitness, they could be considered adaptations to clonal propagation.

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Evolution of the untouchables: Phylogenetics and classification of Cnidoscolus (Euphorbiaceae)

Cited by 10 publications

References 50 publications

Domestication reduces phenotypic plasticity in chaya ( Cnidoscolus aconitifolius (Mill.) I.M. Johnst)

Domestication reduces phenotypic plasticity in chaya ( Cnidoscolus aconitifolius (Mill.) I.M. Johnst)

Distribution, Ecology, Chemistry and Toxicology of Plant Stinging Hairs

Artificial Selection Optimizes Clonality in Chaya (Cnidoscolus Aconitifolius)

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